"In breast cancer, vasoactive intestinal peptide (VIP) is an autocrine growth factor. High densities (100,000/cell) of VIP receptors are present in breast cancer cells. In the present period 18F-VIP conjugates were synthesized and evaluated for biological activity. The VIP conjugates bound with high affinity to T47D cells and elevated cAMP. Also, 18F-VIP localized to breast cancer tumors in nude mice. These results suggest that 18F-VIP may be a useful agent to localize breast cancer tumors using positron emission tomography techniques. Sigma receptors were characterized in breast cancer cells. Sigma ligands such as haloperidol bind to MCF-7 cells with high affinity (Kd = 10 nM). High concentrations of haloperidol (10 uM) elevate cytosolic Ca2++ in MCF-7 cells and inhibit their proliferation. Similar results were obtained for (2-piperidinyl-amino ethyl)-4-iodobenzamide (IPAB), N-(2-piperidino)ethyl)-4-iodobenzamide (4-IBP) and N-[2-(1'-piperidinyl)ethyl]-3-iodo-4-methoxy-benzamide (PIMBA). IPAB, 4-IBP or PIMBA inhibited T47D growth in vitro and breast tumor proliferation in nude mice. These results suggest that sigma ligands may be therapeutic agents for breast cancer."